Thanks for posting in the Apple Support Communities apple2021-2022,
We understand you're seeing a significant decrease in battery performance, and we're happy to offer some guidance we expect to be helpful!
First, if you haven't yet, try using the Activity Monitor app on your Mac to review energy usage and see how power is being used. You can also identify stuck or unresponsive processes, and closing them from there can sometimes offer an improvement. The following guides explain how to do both: Activity Monitor User Guide and View energy consumption in Activity Monitor on Mac
Depending on what you find there, you can also find guidance to get the most out of a charge, here: Maximizing Battery Life and Lifespan
For further assistance, we recommend working with an Apple technical expert who can partner with you to investigate and assist further. To connect with an expert, Contact Apple Support.
Cheers!